The invention relates generally to network communications. More specifically, the invention relates to a system and method of determining whether Synchronous Transport Signal (STS) alarms are associated with a rider service, a child Optical Point of Interface (OPOI) or a parent OPOI in digital signal circuits embedded in Synchronous Optical Networking (SONET), paths.
Wireline telephone companies are divided into two large categories, long distance (IntereXchange Carrier, or IXCs) and local (Local Exchange Carrier, or LECs, also known as Access Providers (APs)). An IXC carries voice and data traffic between telephone exchanges in different Local Access and Transport Areas (LATAs). Most voice traffic is digitized and is typically a data stream which may be intermixed with data traffic for digital data transmission.
There are major savings for an IXC to buy bulk optical access from an AP. In this arrangement, the Point of Interface (POI) between the IXC and AP is optical and is referred to as an Optical POI (OPOI). These OPOIs may carry optical signals such as SONET Synchronous Transport Signals (STS-N) or electrical customer circuits such as Digital Signal (DS3) services.
To maximize IXC economic benefits, a higher rate OPOI using an Optical Carrier (OC) such as OC-48 or OC-192 can carry lower rate OPOIs such as OC-3 or OC-12. This arrangement is known as cascaded OPOIs. Cascaded OPOIs allow an IXC to use OPOI access to AP/LEC end-offices that have IXC/AP traffic volumes insufficient to justify a higher rate OPOI. Unfortunately, the Network Assurance (NA) of a cascaded OPOI is not straightforward, in particular with respect to analysis of autonomous alarms. The goal of an alarm analysis is to determine the entity in trouble, that is the parent OPOI, the child OPOI, rider services on the parent OPOI, or rider services on the child OPOI.
For DS3 circuits carried in these layouts, SONET Network Elements (NEs) associated with the cascaded OPOI do not provide direct visibility to the IXCs for DS3 alarms or Performance Monitoring (PM) parameter data. Typically, there are no DS3 alarms available for a pure switched circuit-based network with an OPOI. However, an alarm on the STS-1 that carries the DS3 indicates that the DS3 has a problem.
An IXC may have bulk optical access, or OPOIs, with an AP. The optical access may be a multi-leveled, cascaded architecture where children OPOIs are located within parent OPOIs. Typical OPOI facilities can support child OPOIs as well as rider services across the parent OPOI. The child OPOIs can also carry additional child OPOIs and rider services. A rider service is an end-to-end STS or DS3 service which uses an OPOI for access to an AP. The rider service has a virtual POI with the AP, the STS-N timeslots on an OPOI versus a physical POI to the AP. The physical POI can be electrical for digital signals or optical for synchronous transport signals. The OPOIs are channelized SONET facilities, carrying STSs at different levels, (STS-N)/(Optical Carrier (OC-X)), where N/X=1, 3, 12, 48, etc. Alarms for a child OPOI and STS-N (non-concatenated) rider services are reflected as a series of STS-1 level alarms, not as a single STS-N alarm. However, for STS-Nc (concatenated) and DS3 rider services, there is just a single STS-1 alarm.
Cascaded optical access can provide a further access savings for an IXC. Cascading OPOIs allow lower bandwidth OPOIs, for example, OC-3, OC-12, to be economically feasible. However, a cascading OPOI needs to be maintained. There is the issue of analyzing and interpreting alarms associated with a cascading OPOI since the alarms arrive on a STS-1 level. An additional complication is the fact that an OPOI can have a cascading OPOI which in turn carries another cascading OPOI.
What is desired is a system and method that allows real-time processing of child OPOI and rider service alarms from a parent OPOI that determines if one or more STS-1 alarms are associated with the rider service, the child OPOI, or the parent OPOI. This would provide needed maintenance capabilities for an IXC to confidently deploy a cascading OPOI by having the service alarm location incorporated in a maintenance ticket or report. Operations personnel can quickly remedy the facility/circuit experiencing trouble instead of spending hours trouble shooting the optical carrier to find which component is failing.